The present invention relates to a substrate washing apparatus and method for scrub-washing a substrate.
In a semiconductor device manufacturing process, a surface of the semiconductor wafer is scrubbed by a brush or a sponge while pouring a cleaning liquid thereon. Since foreign matters such as particles, organic substances, and metals are removed in this manner, the clean level of the surface is enhanced.
To attain the scrub washing, the apparatus disclosed in U.S. Pat. No. 5,685,039 is conventionally used. However, in the conventional apparatus, particles may attach to the surface of a scrub member (brush or sponge) and enter slightly depressed portions and holes in the scrub member. The particles attached to and introduced into the scrub member may fall off from the scrub member, attaching onto a wafer W.
An object of the present invention is to provide a substrate washing apparatus and method employing a scrub member which particles are rarely attached to and which can be easily cleaned.
According to the present invention, there is provided a substrate washing apparatus comprising:
a film scrub member permeable to liquid, which is moved relatively to a substrate held substantially horizontally while being in contact with the substrate;
a supporting portion for supporting the film scrub member;
a supply pipe for supplying a cleaning liquid to the substrate through the film scrub member;
cleaning liquid supply means for supplying the cleaning liquid to the supply pipe;
pressing means for pressing the film scrub member supplied with the cleaning liquid and swollen, to the substrate; and
relative moving means for horizontally moving the film scrub member supplied with the cleaning liquid and swollen, relative to the substrate.
In the substrate washing apparatus, since the film scrub member has a low adsorption force to the particles. It is difficult for the particles to attach to the scrub member. Since the cleaning liquid is allowed to blow out from the film scrub member, it is difficult for the particles to enter the film scrub member. When the film scrub member itself is cleaned, the particles easily fall off from the member, with the result that time required for cleaning can be reduced.
The apparatus of the present invention further comprises a controller for controlling at least one operation of the pressing means and the cleaning liquid supply means. The controller controls an overdrive contact load to be applied to the substrate through the film scrub member by controlling the pressing means.
The apparatus of the present invention further comprises means for adjusting supply pressure for the cleaning liquid flowing through the supply pipe. In this case, the controller adjusts the overdrive contact load applied to the substrate through the film scrub member by controlling the cleaning liquid supply pressure adjusting means.
The supporting portion has a cylinder, a lower portion of which the film scrub member is attached to, an upper portion of which the upper supply pipe is connected to, and which has a reservoir space for temporarily storing the cleaning liquid supplied from the supply pipe and also has driving means for driving the rotation of the cylinder about a vertical axis.
Furthermore, it is preferable that the apparatus of the present invention should have a wafer-flow dispersion plate which is interposed between the reservoir space and the film scrub member and which has a plurality of holes for passing the cleaning liquid from the reservoir space to the film scrub member.
Furthermore, it is preferable that the apparatus of the present invention should have an elastic member (sponge) permeable to water, which is interposed between the reservoir space and the film scrub member, for passing the cleaning liquid from the reservoir space to the film scrub member. As the elastic member (sponge) permeable to water, foamed PVA (polyvinyl alcohol) is preferably employed. In this case, the elastic member is used as a core member of the film scrub member. Even if the supply amount of the cleaning liquid to the film scrub member is low, a desired inner pressure of the film scrub member is obtained, so that consumption of the cleaning liquid is decreased.
It is preferred that the supporting portion has a ultrasonic wave oscillating portion for applying ultrasonic wave to the cleaning liquid passing through the supply pipe. When the cleaning liquid is supplied to the surface of the substrate while oscillating the cleaning liquid by ultrasonic waves, the washing performance and dispersion force are increased.
The film scrub member is formed of a porous and wafer proof resin film or a hydrophilic resin film. As the wafer-proof resin film, a fluoroplastic resin is suitable. As the hydrophilic resin, a polyolefin series resin is suitable. Since these resin has a low abrasion coefficient, it is difficult for the particles to attach the resin. Since resistance to a chemical agent is high, a chemical agent having higher washing performance may be used.
Such a film scrub member is formed as follows: when polytetrafluoroethylene (PTFE) particles are heated and pressed, the particles are partially melted and adhered, thereby forming a hot-press film. Thereafter, appropriate tension is applied to the hot-press film to expand the non-melting portion. As a result, a reticulate tissue having a plurality of fine holes is obtained. The tension is applied to the hot press film either by a uniaxial drawing method (for drawing the film in a single direction (X-axis direction)) or by a biaxial drawing method (for drawing the film in two directions (X-axis and Y axis directions)). In the drawing porous film, it is preferable that a film thickness should fall within the range from 0.5 to 5.0 mm and that an average diameter of the fine holes should fall within the range of 0.1 to 50 xcexcm. In order to provide a necessary tensile strength to the film and let water pass through the fine holes smoothly, it is most preferable that the film thickness should fall within the range of 1.0 to 3.0 mm and the average hole diameter should fall within the range of 0.5 to 2.0 xcexcm.
As a material for the film scrub member, a tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychrolotrifluoroethylene (PCTFE) may be used besides PTFE. Since these fluoroplastic resin materials are water proof, the film must be rendered porous in order to let water through. In order for the film-scrub member not to be broken by water pressure, the tensile strength of the resin film constituting the film scrub member is set at 24.7 kgf/mm2 or more in the drawing direction and 5.9 kgf/mm2 or more in a direction perpendicular to the drawing direction.
On the other hand, a hydrophilic resin such as a polyolefin resin may be used. In the case where the film scrub member is formed of the hydrophilic resin, the lowermost value of the film thickness ensuring a necessary tensile strength, is set at 0.5 mm. There is no uppermost limit of the film thickness. This is because water is easily permeated through the hydrophilic resin film.
According to the present invention, there is provided a substrate washing method comprising the steps of:
(a) holding the substrate substantially horizontally
(b) supplying a cleaning liquid to a surface of the substrate through a film scrub member permeable to liquid and allowing the film scrub member in contact with the surface of the substrate;
(c) pressing the film scrub member onto the surface of the substrate in excess of a zero point, which is an initial contact point of the film scrub member with the surface of the substrate, thereby bringing the film scrub member into contact with the surface of the substrate in an overdriving manner; and
(d) moving the film scrub member relative to the substrate to scrub the surface of the substrate by the film scrub member.
The method of the present invention further comprises the step (e) for allowing a dummy substrate in contact with the film scrub member in the overdriving manner to scrub-wash the dummy substrate, thereby obtaining the most suitable overdrive contact load. In this case, in the step (c), a descending amount of the film scrub member is controlled or a supply pressure for the cleaning liquid is controlled so as to adjust the overdrive contact load of the film scrub member applied to the substrate to the most suitable overdrive contact load obtained in the step (e).
The method of the present invention further comprises the step (e) for allowing a dummy substrate in contact with the film scrub member in the overdriving manner to scrub-wash the dummy substrate, thereby obtaining the most suitable overdrive contact load. In this case, in the step (c), a descending amount of the film scrub member is controlled and a supply pressure for the cleaning liquid is controlled so as to adjust the overdrive contact load of the film scrub member applied to the substrate to the most suitable overdrive contact load obtained in the step (e).
In the steps (c) and (d), the supply pressure for the cleaning liquid may be substantially equal, set larger than that applied at non-operation time during which the substrate is scrub washed, or changed depending upon a surface state of the substrate.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by-means of the instrumentalities and combinations particularly pointed out hereinafter.